Non-Woven Poly 6 Mil - Blackout - 25' x 100'The Blackout Greenhouse poly ensures no light will reach your plants until you want it to! Blackout Poly is the ideal covering for light deprivation greenhouse setups and is black on one side with a reflective white outer layer to further prevent light penetration. Using blackout poly on your greenhouse is found to result in improved production and increased plant yield that comes from growing year round regardless of weather conditions, and it is